law enforcement officials tell abc news 19-year-old suspect dzhokhar tsarnaev is awake. he's unable to speak because of a neck injury authorities believe may be self-inflicted. tsarnaev is answering some questions in writing. we're told authorities asked about potential accomplices and any unexploded bombs. >> i am not convinced they were planning more attacks. that's hearsay. i haven't got information about that. but, you know, we have to be vigilant. >> reporter: since police captured him after a dramatic d to friday's mat, the brder investigfocuses on his older brother. 26-year-old tamerlan died in a shootout with police. last year, he traveled overseas to russia and chechnya and began linking to jihadist videos online. some wonder why he fell off the fbi's radar after they questioned him about possible terror ties two years ago. >> somehow, he got off the radar screen and traveled overseas to one of the most dangerous parts of the world. >> reporter: the bombings left three dead and dozens injured. many are still in the hospital. yesterday, boston remembered the vict